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In DeltaABC, prove that: sin^(2)A+sin^...

In `DeltaABC`, prove that:
`sin^(2)A+sin^(2)B+sin^(2)C`
`=1-cos^(2)A+sin^(2)B+1-cos^(2)C`
`=2-cos(A+B)cos(A-B)-cos^(2)C`
`=2-cos(180^(@)-C)cos(A-B)-cosC.coc{180^(@)-(A+B)}`
`=2+cosC.cos(A-B)+cos(A+B)]`
`=2+cosC.2cosAcosB`
=RHS Hence proved.

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